ABSTRACT Virtually every aspect of T cell function depends on regulated changes in actin dynamics. I have recently shown that the Abelson kinase c-Abl is required for appropriate actin responses in T cell activation and migration. In keeping with this, evidence from studies using c-Abl-deficient mice and clinical studies of patients treated with the Abl inhibitor imatinib indicate that Abl kinase function is required for effective T cell-mediated immunity. However, little is known about the normal role of c-Abl in T cells. My long-term career goal is to establish my own research niche, with a research program revolving around understanding c-Abl function in the immune system. My immediate goal is to test the hypothesis that c-Abl regulates T cell activation by regulating the function of the actin-associated proteins HS1 and WAVE2. To test this hypothesis, I will conduct three specific aims: 1) Since localization is a key mechanism by which c-Abl function is regulated, I will image c-Abl recruitment and activation at the immunological synapse (IS), and analyze the domains that regulate c- Abl localization in T cells. 2) To understand how c-Abl regulates HS1 activity, I will identify the sites where c- Abl phosphorylates HS1, and assess the functional consequences of this phosphorylation. In addition, I will analyze the spatial and functional interaction of c-Abl and HS1 in living T cells. 3) To understand how c-Abl interacts with WAVE2, I will ask if c-Abl phosphorylates WAVE2 or WAVE complex components, and analyze the regulatory role of c-Abl on WAVE2 localization in living T cells. These studies will be conducted in Dr. Janis Burkhardt's lab, and will draw upon the outstanding research environment in her lab and at the Children's Hospital of Philadelphia and University of Pennsylvania. I anticipate that by carrying out this project, I will gain valuable experience in studying primary T cell responses. In particular, I plan to use a combination of advanced imaging and protein analytical tools to address the problem of T cell signaling at the level of protein dynamics and signaling complex formation. This will help me to move into important and understudied areas of T cell signaling, and will form the foundation for my independent research program.